My personal favorite feature in Halo 2 is the ability to steal vehicles. This addition to the gameplay has totally changed the vehicle strategy of the original Halo. In the original, vehicles were almost unstoppable. It was very difficult to beat someone who was in a vehicle when all you had was the pistol and a few HE grenades. Also the vehicles could not be destroyed and some were not usable by the player.
In Halo 2 the tables have been turned. All the vehicles (with the exception of some of the transport ships and the scarab) can be used by the player. Also every vehicle now takes damage and can be destroyed. The best way to fend off a vehicle is to take it. When the vehicle approaches you hold down the x-button. Depending on the vehicle, you either pull the enemy off, or you can punch or grenade them. This is an excellent way to get a quick advantage; also in multiplayer it will score you a metal.